Interferons (IFNs) are members of a large family of extracellular proteins that mediate anti-tumor, immunomodulatory, anti-viral and anti-microbial actions. It is now clear that paradigms for intracellular signaling, developed using the IFN systems as models, are broadly applicable to many other molecules that, individually and in combination, regulate cell growth, differentiation, and inflammation. Study of the signaling events that mediate the diverse biological effects of IFNs has identified families of gene products that collectively transduce the signals not only from IFNs but also from many other stimuli. The work supported by this program project grant has led to significant contributions in developing this body of information, particularly through the application of forward genetics in mammalian cells. The overall theme of the renewal application focuses on the diverse mechanisms through which a relatively limited set of gene products generates the highly diverse array of biologic responses necessary to prevent the development and/or spread of cancer. The specific experimental targets include proteins that mediate the immediate signals in response to IFNs and other cytokines, including novel activities of JAKs and STATs, signaling molecules that are not JAKs or STATs, and downstream effectors responsible for biological outcomes. The experiments will utilize genetic, biochemical and molecular biological strategies to determine the functions of and interactions between individual protein targets. Project 1 will investigate signaling in response to TNF- alpha, study stimulus-independent activities of STAT1 and continue to explore new routes of IFN action that control the expression of the proto- oncogene, c-myc. In Project 2, the roles of cytosolic phospholipase A2, the double stranded RNA-dependent protein kinase PKR, and the protein tyrosine phosphatase SHP-1 in cytokine signaling will be further elaborated. Project 3 will be focused upon a navel signaling pathway responsible for IFNbeta-specific responses. Project 4 will expand upon the exciting finding that the IFN-inducible RNAse L system can be used to destroy tumors cells selectively by targeting the degradation of the RNA component of telomerase, which is necessary for immortalization of cancer cells. Project 5 will address the roles of dsRNA binding proteins in the control of IFN-inducible gene expression. Project 6 will define the molecular events associated with the inhibitory control of IFN-inducible gene expression by the anti-inflammatory cytokine IL-4. In sum, these interrelated and cooperative activities will further our knowledge of several signaling pathways that are important in cancer.